Single sided will sound just as good if the jumper links are kept to a minimum, and if the ones that you absolutely must use are routed properly. Double sided is just easier to work with when you are getting your boards professionally manufactured.

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"Audio grade" components simply means that they failed at a more critical job.

Decoupling is located too far from the power pins. The HF section of Cs1&2 can be 0.1" or 0.2" pin pitch. The smaller can be located right on top of the power and ground pins. Or even underneath if that suits you and aesthetics.

Although very commonly used as a solution, I do not like distance between the Vdd & Vcc lines. I recommend that the Power Lines and the Power Return be fed in, very close to each other.
The speaker output trace could be doubled or even tripled in width.
Add a bigger pad around Pin1 (Vcc). Is Pin5 also Vcc?

You have not implemented the unmute function. This will never allow the amp to turn on!!!

You have no specific connection for Signal Return/Ground. It is shared with Power Ground and Speaker Return. Isolate the Signal Returns on the PCB and give them a dedicated Signal Ground. Signal Hot and Signal Return connect directly to the input signal hot and cold at the chassis input socket

Rm seems redundant. It is normally there before the DC blocking cap to ensure the PCB input pin is always close to Zero Volts. But you have chosen to omit the DC blocking cap, so Rm should be omitted as well.

Spkr Return on the PCB works for a single channel monoblock amplifier.

When you have more than one channel inside the same chassis, all the Returns should meet at the Main Audio Ground (MAG). This cannot be on one of the amplifier PCBs.

That's all I can see, I hope the list does not get any longer,

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regards Andrew T.
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Regarding the grounding issue, CHG is the “star” ground that I then take to a central point on the chassis which I was going to use as my MAG.

Quote:

You have no specific connection for Signal Return/Ground. It is shared with Power Ground and Speaker Return. Isolate the Signal Returns on the PCB and give them a dedicated Signal Ground. Signal Hot and Signal Return connect directly to the input signal hot and cold at the chassis input socket

Do you mean that Vcc and Vdd stay as they are, with Speaker, IP and OP ground becoming an Isolated signal ground. Does this then earth via the chassis input?

That looks decent. You could add a corner in the output trace so it doesn't sit so close to the one connecting R3 and Ci.

All grounds must always be connected together, it's the routing that matters. Power ground should have a separate trace from input ground, that's what everyone says, but let me elaborate on it. Chassis ground should always be connected to input ground, right where the input wire connects to the board. If you connect the chassis ground to the ground of the filter caps (common mistake) you will get hum.

On the other hand, you have created a board with planes. You don't need to separate anything because you basically have solid planes of ground and power. I've yet to have a board made like that exhibit any kind of hum. So don't waste anymore time and build it. One thing i would do would be to route that output trace to the left where it meets Rz, to allow more of the ground plane to connect both sides. It's looking good otherwise.

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"Audio grade" components simply means that they failed at a more critical job.

RF attenuator is a lowpass filter with a high cutoff frequency (some 100s of khz), placed at the input. Basically a small capacitor (some 10s of picofarads) across the input resistor. It isn't needed if you're driving the amp from a low impedance source such as an opamp.

In other words, if you also have an input stage for your amplifier you don't need it. If the amp input is accessible directly to the outside world it is recommended to fit it.

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"Audio grade" components simply means that they failed at a more critical job.

I believe that every input must have a filter to attenuate what is not supposed to be there.
My home has only one transmitter, my mobile phone.
Many homes have literally a dozen transmitters polluting the airspace.
Keep it out !!!

__________________
regards Andrew T.
Sent from my desktop computer using a keyboard